Android Arraylist迭代设置或添加基于它是否存在

我希望能够检查一个对象是否存在，根据其_sensor_id内ArrayList它显示在ListView。Android Arraylist迭代设置或添加基于它是否存在

如果存在，我想设置它，如果不存在，我想添加它。每次此方法运行时，HashMap数据都会不同，我希望它根据_sensor_id来检查它是否存在于ListView（ArrayList）中或不存在。

if (mEquipmentList.isEmpty()) { 
// Populate the Equipment List 
HashMap < String, String > equip = new HashMap < String, String >(); 
equip.put(FIRST_COLUMN, _sensor_id); 
equip.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
equip.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
equip.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
equip.put(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 
mEquipmentList.add(equip); 

for (HashMap < String, String > entry: mEquipmentList) { 
    for (String key: entry.keySet()) { 
    String value = entry.get(key); 
    //Debugging 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList.get(0)); 
    Log.d("equipment key = ", "key: " + key); 
    Log.d("equipment value = ", "value: " + value); 
    Log.d("equipment index", "value:" + (mEquipmentList.indexOf(equip))); 
    } 
} 
} else { 

// Populate the Equipment List 
HashMap < String, String > equip = new HashMap < String, String >(); 
equip.put(FIRST_COLUMN, _sensor_id); 
equip.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
equip.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
equip.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
equip.put(SECOND_COLUMN, Double.toString(mEquipmentList.size())); 
mEquipmentList.set(0, equip); 

for (HashMap < String, String > entry: mEquipmentList) { 
    for (String key: entry.keySet()) { 
    String value = entry.get(key); 
    //Debugging 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList); 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList.contains(key)); 
    Log.d("equipment key = ", "key: " + key); 
    Log.d("equipment value = ", "value: " + value); 
    Log.d("equipment index", "value:" + mEquipmentList.indexOf(equip)); 
    } 
} 
} 

// Set the adapter 
ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
listView.setAdapter(adapter); 
adapter.notifyDataSetChanged(); 

}

编辑*********

public void updateEquipList(String message) { 

    if (!pathHistory.isEmpty()) { 
     double currentLat = pathHistory.getFirst().lat; 
     double currentLng = pathHistory.getFirst().lng; 
     int currentOrientation = getResources().getConfiguration().orientation; 

     ListView listView = (ListView) findViewById(R.id.equip_list); 

     HashMap<String, Equipment> equipmentMap = new HashMap<String, Equipment>(); 

     try { 
      List<String> data_list = Arrays.asList(message.split(",")); 

      // point added (checks in correct format) 
      String _sensor_id = data_list.get(0); 
      if (_sensor_id.substring(0, Math.min(_sensor_id.length(), 2)).equals("DT")) { 

       double _lat = Double.parseDouble(data_list.get(3)); 
       double _lng = Double.parseDouble(data_list.get(4)); 
       double _heading = Double.parseDouble(data_list.get(5)); 
       double _speed = Double.parseDouble(data_list.get(6)); 
       int distance = (int) Trajectory.ChordLength(currentLat, currentLng, _lat, _lng); 
       boolean doesSensorExist = false; 

       // for input _sensor_id, check if there exists an Equipment object in map. 
       Equipment equip = equipmentMap.get(_sensor_id); 
       if(equip == null) // no object for this sensor_id 
       { 
        equip = new Equipment(); 
        // populate equipment attributes in the object 
        equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
        equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
        equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
        equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

        // add this Equipment Object in the map. 
        equipmentMap.put(_sensor_id, equip); 
        /// since its a new object, add same to the mEquipmentList which is a unique array of Equipment Object 
        mEquipmentList.add(equip); 
       } 
       else // Equipment object exits for input _sensor_id string 
       { 
        //Update the values for eq object if they are changed 
        equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
        equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
        equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
        equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 
        // here no need to add the Equipment Object in the ArrayList again. 
       } 

       // Set the adapter 
       ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
       listView.setAdapter(adapter); 

       } 
      } catch(Exception e){ 
       // Marker construction failed 
       Log.d(TAG, "Updating list failed: " + e.toString()); 
      } 
     } 

    } 

class Equipment extends HashMap<String, String> { 
    HashMap<String, String> parameters; 

    void addParameter(String key, String value) 
    { 
     parameters.put(key, value); 
    } 
}

列表视图ADAPTER

公共类ListViewAdapter延伸BaseAdapter {

public ArrayList<com.bhp.prox_aware.MapsActivity.Equipment> list; 
Activity MapsActivity; 
TextView txtFirst; 
TextView txtSecond; 
TextView txtThird; 
TextView txtFourth; 
TextView txtFifth; 

public ListViewAdapter(Activity activity, ArrayList<com.bhp.prox_aware.MapsActivity.Equipment> list){ 
    super(); 
    this.MapsActivity=activity; 
    this.list=list; 
} 

@Override 
public int getCount() { 
    // TODO Auto-generated method stub 
    return list.size(); 
} 

@Override 
public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return list.get(position); 
} 

@Override 
public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return 0; 
} 



@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    // TODO Auto-generated method stub 

    LayoutInflater inflater=MapsActivity.getLayoutInflater(); 

    if(convertView == null){ 

     convertView=inflater.inflate(R.layout.equip_row, null); 


     /* TODO add an ImageView here for an icon to display next to the list */ 
     txtFirst=(TextView) convertView.findViewById(R.id.name); 
     txtSecond=(TextView) convertView.findViewById(R.id.id); 
     txtThird=(TextView) convertView.findViewById(R.id.speed); 
     txtFourth=(TextView) convertView.findViewById(R.id.direction); 
     txtFifth=(TextView) convertView.findViewById(R.id.distance); 
    } 

    int color = Color.argb(200, 34, 34, 34); 


    HashMap<String, String> map=list.get(position); 
    txtFirst.setText(map.get(FIRST_COLUMN)); 
    txtSecond.setText(map.get(SECOND_COLUMN)); 
    txtThird.setText(map.get(THIRD_COLUMN)); 
    txtFourth.setText(map.get(FOURTH_COLUMN)); 
    txtFifth.setText(map.get(FIFTH_COLUMN)); 

    //Check if within 100m if yes change colour of background to red 
    double distanceCheck = Double.parseDouble(map.get(FIFTH_COLUMN).replace("m", "")); 
    if(distanceCheck <= 100){ 

     color = Color.argb(200, 163, 0, 0); 
    }else { 
     color = Color.argb(200, 34, 34, 34); 
    } 

    txtFirst.setTextColor(Color.WHITE); 
    txtFirst.setBackgroundColor(color); 

    txtSecond.setTextColor(Color.WHITE); 
    txtSecond.setBackgroundColor(color); 

    txtThird.setTextColor(Color.WHITE); 
    txtThird.setBackgroundColor(color); 

    txtFourth.setTextColor(Color.WHITE); 
    txtFourth.setBackgroundColor(color); 

    txtFifth.setTextColor(Color.WHITE); 
    txtFifth.setBackgroundColor(color); 

    return convertView; 
}

}

来源

2017-08-24 allen simpson

你应该能够模拟你的代码结构略有不同如果可能创建一个类说用的设备属性存储列参数，如速度，温度等作为地图字符串，Stringthat类

class Equipment 
{ 
    HashMap<String, String> parameters; 

    void addParameter(String key, String value) 
    { 
    parameters.put(key, value); 
    } 
}

在你的逻辑，sensor_id的关键是保持的唯一性设备对象。因此，创建地图字符串的装备

HashMap<String, Equipment> equipmentMap = new HashMap<String, Equipment>(); 
// for input _sensor_id, check if there exists an Equipment object in map. 
Equipment equip = sensorMap.get(_sensor_id); 
if(equip == null) // no object for this sensor_id 
{ 
    equip = new Equipment(); 
    // populate equipment attributes in the object 
    equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
    equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
    equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
    equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

    // add this Equipment Object in the map. 
    sensorMap.put(_sensor_id, equip); 
/// since its a new object, add same to the mEquipmentList which is a unique array of Equipment Object 
    mEquipmentList.add(eq); 
} 
else // Equipment object exits for input _sensor_id string 
{ 
    //Update the values for eq object if they are changed 
    equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
    equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
    equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
    equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

    // here no need to add the Equipment Object in the ArrayList again. 
} 
// notify adapter for data change 
adapter.notifyDataSetChanged();

HashMap中有助于保持基于_sensor_id数据的唯一性。

希望这有助于..

来源

2017-08-24 05:06:40 milindmb

这似乎是它可能是最好的方式来做到这一点，但我不完全知道如何构造它，请你给一个更详细的例子吗？ –

编辑我的答案更多细节。如果你想了解更多的细节，请分享一些更多的代码，以便我更好地理解逻辑。 – milindmb

感谢您的帮助milindmb，我添加了你所做的，但我的listview不再显示。我添加了该列表视图的其他特定代码。 –

我设法得到它的工作执行以下操作，虽然我相当肯定有这样做的更好的方法。

if (currentOrientation == 2 && mSettings.get(0)) { 
        if (mEquipmentList.isEmpty()) { 
         // Populate the Equipment List 
         HashMap<String, String> map = new HashMap<String, String>(); 
         map.put(FIRST_COLUMN, _sensor_id); 
         map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
         map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
         map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
         mEquipmentList.add(map); 
        } else { 

         for (HashMap<String, String> test : mEquipmentList) { 
          if (test.get(FIRST_COLUMN).equals(_sensor_id)) { 
           HashMap<String, String> map = new HashMap<String, String>(); 
           map.put(FIRST_COLUMN, _sensor_id); 
           map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
           map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
           map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
           mEquipmentList.set(mEquipmentList.indexOf(test), map); 
           doesSensorExist = true; 
          } 
         } 
         if (!doesSensorExist && mEquipmentList.size() < 5) { 
          HashMap<String, String> map = new HashMap<String, String>(); 
          map.put(FIRST_COLUMN, _sensor_id); 
          map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
          map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
          map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
          mEquipmentList.add(map); 
         } 
        } 
          // Set the adapter 
          ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
          listView.setAdapter(adapter); 
          adapter.notifyDataSetChanged(); 
        } 
       }

来源

2017-08-28 03:15:51

Android Arraylist迭代设置或添加基于它是否存在

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